SusceptibiIity to the development of asthma and other atopic diseases is known to be associated with genetic components, and several candidate genes have been reported to be linked to atopy and asthma. We have examined a linkage between traits of specific IgE responses to the house dust mite and its purified aller- gens, high total serum IgE levels and asthma, and the markers at the T-cell receptor (TCR) alpha chain gene (TCR-alpha) and beta chain gene (TCR-beta) in Japanese families ascertained through asthmatic children. Affected sib- pair analyses provided evidence for linkage between TCR-beta and nearby markers (D7S684) on chromosome 7q35 and both IgE and asthmatic phenotypes, but no evidence for linkage of IgE responses nor asthma phe- notype to TCR-alpha was detected The results suggest the presence of major gene(s) controlling atopy and asthma susceptibility in TCR-beta and the nearby region.